The present invention relates to an automatic cut-sheet feeder for use with a printer.
Automatic cut-sheet feeders are combined with printers for allowing the printers to print separate sheets successively. More specifically, the automatic cut-sheet feeder operates to supply separate sheets automatically to the printer and discharge printed sheets from the printer.
The automatic cut-sheet feeder is composed of a hopper for extracting one cut sheet at a time from a sheet stack, a feed guide for guiding the extracted cut sheet to a platen in the printer, and a stacker for discharging and stacking cut sheets printed by the printer.
The cut sheets are automatically delivered one at a time from the hopper in response to a feed-in command signal. The cut sheet thus delivered passes through the feed guide and is turned around the platen from a position rearward and downward of the platen toward a position forward of the platen. After the cut sheet has been printed by a print head of the printer, it is delivered from a position forward and upward of the platen toward the stacker of the automatic cut-sheet feeder.
The print head is positioned in front of the platen for printing the cut sheet when it is disposed around the platen across the front surface thereof.
With the conventional cut-sheet feeder, the leading end of the cut sheet as it is turned around the platen is separated from the platen in a front region of the platen, i.e., a region where the print head is moved.
According to one proposal disclosed in U.S. Pat. No. 4,396,307, the cut sheet is pressed against the platen by pressure rollers, which are required to be moved off the platen when the leading end of the cut sheet reaches the pressure rollers, thus providing a clearance allowing the cut sheet to pass therethrough. The pressure rollers are moved in the opening and closing directions by an electromagnet and a link mechanism, which are mechanically and electrically coupled to the printer through a complex arrangement.
U.S. Pat. No. 4,438,915 discloses guide plates 26, 26' disposed in prescribed positions. With this prior arrangement, however, where a cut sheet of a different width or a greater width is used, the leading end of the cut sheet tends to be caught in an area where the guide plates are not present, with the result that the cut sheet may not be fed into the stacker of the cut-sheet feeder.
To eliminate the above drawback, the prior cut-sheet feeder has an upper sheet guide for guiding the leading end of the cut sheet. The upper sheet guide has a width equal to or larger than the width of the cut sheet so as to cover the platen thereabove. The printed cut sheet can be delivered through the upper sheet guide toward the stacker.
Since the upper sheet guide serves to guide the leading end of the cut sheet, it is positioned very closely to the platen. Inasmuch as the print head is also located closely to the platen, the upper sheet guide and the print head are positioned closely to each other. Such a positional arrangement is problematic since the upper sheet guide becomes an obstacle to the replacement of an ink ribbon cassette on the print head, and hence the ink ribbon cassette cannot be replaced with a new one highly efficiently.